Question

A dietary survey report indicates that the 5-year survival rate for breast cancer has increased following the introduction of a new screening method. However, autopsy data shows no change in overall mortality. What type of bias does this scenario illustrate?

• A. Survival bias
• B. Lead time bias
• C. Berksonian bias
• D. Detection bias

Hint:

Screening may increase measured survival time without reducing mortality. This is called lead time bias.

Answer 1

The Correct Option is B

Concept: Lead time bias occurs when screening detects disease earlier, making survival time appear longer even though the actual time of death is unchanged.

Step 1: Understand what screening changes.
Screening detects breast cancer earlier than clinical presentation.

Step 2: Understand why survival appears increased.
The patient appears to survive longer from the time of diagnosis because diagnosis occurred earlier.

Step 3: Check mortality.
Since overall mortality is unchanged, the apparent survival improvement is due to: \[ \text{Lead time bias} \]